Problem: Vanessa is 3 times as old as Umaima and is also 12 years older than Umaima. How old is Vanessa?
Answer: We can use the given information to write down two equations that describe the ages of Vanessa and Umaima. Let Vanessa's current age be $v$ and Umaima's current age be $u$ $v = 3u$ $v = u + 12$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $v$ is to solve the second equation for $u$ and substitute that value into the first equation. Solving our second equation for $u$ , we get: $u = v - 12$ . Substituting this into our first equation, we get the equation: $v = 3$ $(v - 12)$ which combines the information about $v$ from both of our original equations. Simplifying the right side of this equation, we get: $v = 3v - 36$ Solving for $v$ , we get: $2 v = 36$ $v = 18$.